The use of a supercharger to increase or “boost” the air pressure in the intake manifold of an internal combustion engine to result in an engine having a greater horsepower output capability is generally known. The engine may thus have an increased horsepower output capability than would otherwise occur if the engine were normally aspirated (e.g., the piston would draw air into the cylinder during the intake stroke of the piston). A conventional supercharger is generally mechanically driven by the engine, and therefore, may represent a drain on engine horsepower whenever engine “boost” may not be required and/or desired. Some sort of engageable/disengageable clutch may be disposed in series between the supercharger input (e.g., a belt driven pulley) and the rotors of the supercharger.
There are three basic types of clutch assembly configurations and/or designs: (1) a large pulley configuration; (2) a small pulley configuration; and (3) a remote mount clutch configuration. While each of these three basic types of clutch assemblies can operate in a commercially acceptable and satisfactory manner, there may be potential disadvantages associated with each type of the above-referenced clutch assemblies. With respect to a large pulley configuration, for example, the pulley is generally integrated to the rotor, and the pulley is of a large enough diameter so as to fit over a clutch coil that is mounted to the supercharger cover. Because the pulley is integrated to the rotor, the pulley design is dependent on the torque capacity of the clutch. In other words, the pulley diameter must be increased if the torque capacity of the clutch is increased. This results in undesirable packaging requirements because the required pulley diameters are typically too large to be commercially feasible. In addition, a large pulley has high inertia. With respect to a small pulley configuration, the pulley design may not be dependent on the size of the clutch coil. However, the pulley is generally integrated with the clutch armature. Because the clutch armature is fixed to the pulley, the clutch armature is generally rotating at the speed of the pulley even when the clutch is disengaged, and the armature may not be particularly stable at higher speeds. In addition, in some configurations, the bearings may have an increased bearing load, and the absence of relative motion between the inner and outer race of the bearing when the clutch is in an engaged position may put additional stress and/or load on the bearings. This may allow damage (e.g., fretting) to the bearings. The fretting becomes an issue due to the belt loads that must be supported by the stationary bearing. Finally, with respect to a remote-mount pulley configuration, the pulley has the highest inertia associated with putting the clutch in an engaged position.